1. Field of the Invention
The present invention relates to image processing methods and apparatus useful, for example, in examining essentially two-dimensional surfaces. More specifically, the invention relates to such image processing methods and techniques which may be used to identify and account for distortion in the image relative to an idealized version of the image.
2. Description of the Related Art
The image processing method and apparatus of the invention have potential application in a number of areas. They are potentially applicable to virtually any image processing application in which the image to be analyzed is subject to distortion relative to an idealized version of the image. The method and apparatus are particularly useful, for example, in the printing and engraving industries where they may be used in such applications as quality control. The need for refined image processing is especially pronounced in printing applications wherein the actual printing is carried out by applying pressure to the printed substrate or specimen. The Intaglio printing process widely used in the fabrication of paper currencies is an illustrative example. In these types of printing applications, the pressure applied during the printing process causes the printed substrate or specimen to become distorted. These distortions may occur in localized regions of the image, or they may extend across substantial portions of the specimen. Quality control measures typically are employed to separate and discard the excessively distorted or flawed specimens. Distinguishing between slight distortions and other more serious defects in the resultant specimen and its image relative to the desired ideal image has been a longstanding problem.
Historically, the task of identifying impermissible distortions and removing defective specimens in the currency printing industry has been manually performed by human inspectors. This has been a relatively slow, inefficient, and costly procedure. A pronounced trend therefore has developed in recent years to automate this quality control procedure. With today's high-speed printing processes, however, and in view of the substantial computational requirements of many real-time or near real-time image processing methods designed to accommodate small amounts of distortion, the ability to automate these more demanding processes has been limited.
3. Objects of the Invention
Accordingly, an object of the present invention is to provide an image processing method and apparatus for detecting and measuring distortion in an image relative to an idealized version of the image.
Another object of the invention is to provide an image processing method and apparatus which offer the potential for detecting relative fine levels of distortion.
Another object of the invention is to provide an image processing method and apparatus which offer the potential for relatively high speed processing of images which include distortions.
Another object of the invention is to provide an image processing method and apparatus which enable relative efficient and low cost processing of images which include distortions.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations pointed out in the appended claims.